The present invention relates to catalysts used for ester metathesis.
Esterification products, and in particular, polyesters (e.g., polyethylene terephthalate or PET, PEN, polyester oligomers, liquid crystal polyesters, and PBT), along with polycarbonates, are used in a vast array of products. Such products include, for example, cotton-blended fabrics, wool-blended fabrics, recording media, reinforced plastics, and thermoplastic elastomers. Additionally, polyesters are being increasingly used in beverage bottles.
Ester-containing materials (e.g., polymers) are often prepared commercially by a transesterification reaction involving ester monomers, oligomers, polymers, etc. and alcohols. In such a reaction, catalysts containing metals such as manganese, calcium, zinc, tin, titanium, and the like have typically been employed. These catalysts, however, suffer from several drawbacks. Rates of reaction using such materials are typically slow and thus often limit the rate of producing polyester-containing end products.
Additionally, trace amounts of the catalyst are often present in the polyester material upon completion of the reaction. Residual catalyst traces may trigger ongoing transesterification when the starting material is subjected to heat such as during processes involving extrusion, molding, and the like. This is undesirable since it potentially adversely affects physical properties of resulting end products. Accordingly, the presence of a catalyst deactivator (additive) is often required. Moreover, the presence of residual catalyst traces is highly disadvantageous when polyester is used in consumer products such as soft drink bottles, since these metals have the ability to leech into the liquid. Thus, the catalysts may be potentially hazardous from a biological standpoint.
In view of the above, it is an object of the present invention to provide for a catalyst for use in forming esterification products which provides for faster rates of reaction and is potentially more biologically acceptable than previous catalysts.